The reason IBOC AM radio is problematic at night is exactly the same reason why any idea of high fidelity AM radio, which covers 30 KHz of spectrum instead of only 10 KHz, is a problem at night. These 30 KHz stations spill over into the frequency allocations of other AM stations (which are spaced 10 KHz apart). At night, when AM propagates long distances, this causes interference for anyone not completely dominated by the broadband station's signal. Translated, this creates annoying squeals for anyone trying to tune his AM radio to a somewhat weak signal, especially at night. IBOC AM radio places the digital content in two bands adjacent to the central 10 KHz analog AM station. Together, these two bands and the analog take up 30 KHz vs 10 KHz for analog stations. (Wideband analog AM also uses 30 KHz of spectrum, so its should come as no surprise that this creates the same problem.) IBOC FM does something similar, taking up 400 KHz for an IBOC FM station, compared with the 200 KHz assigned to an analog FM station. The advantage is that FM stations only propagate so far, day or night (if we ignore the occasional skip). So if this works during the day, it will also work at night. Seems to me that ATSC could also have been called "IBOC." In the sense that stations are assigned what would otherwise have been considered tabboo frequencies for transmission of their digital signal. For instance, in principle, TV stations could have been assigned the immediately adjacent channel for their DTV signal. Some of the time, this might actually have worked. I'm really not sure I see the difference between this and IBOC radio, with respect to the term "IBOC" (in band, on channel)? Bert -------------------------------------- TI bets on chips to amplify digital radio market By Junko Yoshida , EE Times July 22, 2004 (10:31 AM EDT) URL: http://www.eet.com/article/showArticle.jhtml?articleId=3D23904934 Paris - The emerging U.S. terrestrial digital radio market will get a substantial boost this week when Texas Instruments Inc. rolls out two HD Radio baseband processors that make up its third-generation digital radio silicon. One chip will allow radio manufacturers to add digital terrestrial HD Radio to existing analog AM/FM radio designs; the other supports HD Radio and analog AM/FM radio in a single chip. The sampling price of each chip is $22 per unit. John Gardner, digital radio marketing manager at TI, called the TMS320DR350, which combines IF-sampled AM/FM and HD Radio processing, "the industry's lowest-cost implementation of HD Radio technology." Many consider cost reduction an imperative for HD Radio to boom. The rollout of HD Radio technology by iBiquity Digital Corp., the developer of the U.S. terrestrial digital broadcast system-called in-band on-channel (IBOC)-has encountered a number of obstacles over the last few years. iBiquity is the sole owner of intellectual property for IBOC; TI is an investor in iBiquity. The difficulties include iBiquity's last-minute switch of the IBOC codec last summer to improve audio quality (see www.eet.com/showArticle.jhtml?articleID=3D18309105); reduced coverage and interference with adjacent analog channels reported by a group of radio engineers, station owners and others; and interference with nighttime AM broadcasts. While iBiquity's IBOC technology has been approved by the Federal Communications Commission for digital broadcasts by existing AM and FM radio stations, the FCC hasn't yet approved digital nighttime transmissions by AM stations due to interference concerns. The FCC is accepting public comment on interference until Aug. 2, but the delay and uncertainty over nighttime broadcasts has crimped HD Radio's potential reach. Nighttime AM IBOC broadcasts are "a fly in the ointment," said Will Strauss, president of Forward Concepts Co. (Tempe, Ariz.). Critics argue that sidebands might wipe out weak distant radio stations, Strauss said, "and there are a lot of people who simply like to log reception of distance, or DX, broadcasts." The installed base for HD Radio in the United States is "very, very limited," said Dan Benjamin, analyst at ABI Research Inc. (Oyster Bay, N.Y.), "as just a handful of devices are even available and those devices remain very expensive, on the order of several hundred dollars." Analyst Strauss agreed, estimating shipments of "only about 30,000 radios" for 2004. Assuming approval of nighttime AM IBOC late this year, Strauss said, "We expect 2005 will only see factory-installed IBOC-capable radios in the 100,000 range." Forward Concepts doesn't expect the HD Radio market to hit a million units before 2007. That may explain chip makers' scant interest in HD Radio. Only TI and Philips Semiconductors now offer HD Radio chips. Beyond the imperative to cut costs, the industry agrees, HD Radio also needs more features. Samples of TI's DRI350 and DRI300 HD Radio basebands are available now, with volume production scheduled in the fourth quarter. Copyright 2003 CMP Media ---------------------------------------------------------------------- You can UNSUBSCRIBE from the OpenDTV list in two ways: - Using the UNSUBSCRIBE command in your user configuration settings at FreeLists.org - By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word unsubscribe in the subject line.